1. Field of the Invention
This invention relates to an image pickup lens and an image pickup apparatus. Specifically, the present invention relates to a technical field of a large aperture single focus lens as an image pickup lens which has an F number of approximately 1.2 to 1.5 and an angle of view of approximately 46 degrees and can be used suitably with a camera with an interchangeable lens, a video camera, a digital still camera, a broadcasting camera and so forth and an image pickup apparatus which includes a large aperture single focus lens.
2. Description of the Related Art
A large aperture lens having an F number of approximately 1.2 to 1.5 is used as an image pickup lens. Most of such large aperture lenses have a double Gauss configuration wherein two combinations of a concave lens and a convex lens are disposed in an opposing symmetrical relationship with each other. Since such large aperture lenses use full extension type focusing, most of them exhibit significant deterioration of an image formation performance upon short range image pickup.
Meanwhile, a retrofocus type lens which uses a floating system for moving a plurality of lens groups at different speeds upon focusing is adopted as a large aperture wide angle lens having an angle of view of approximately 64 degrees.
As an image pickup lens which uses such a floating system as just described, for example, an image pickup lens is known which is configured from a first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power. An image pickup lens of the type just described is disclosed, for example, in Japanese Patent Laid-Open No. Sho 63-61214 (hereinafter referred to as Patent Document 1).
The image pickup lens disclosed in Patent Document 1 is of the retrofocus type which employs the floating system, and is adopted, for example, in a large aperture wide angle lens having an angle of view of approximately 64 degrees.
The image pickup lens disclosed in Patent Document 1 uses the floating system wherein, when the image pickup object distance varies from the infinity to the proximity, the first lens group is fixed with respect to an image surface while the second lens group moves from the image side toward the object side and the third lens group moves from the image side toward the object side while varying the distance to the second lens group.
Meanwhile, as a large aperture intermediate telephoto lens of an angle of view of approximately 29 degrees, a lens is known in which a first lens group including two positive lenses and a strong negative lens having a concave face directed to the image side are disposed in order from the object side toward the image side and which has a positive refracting power, and a second lens group having a positive refracting power. A large aperture intermediate telephoto lens of the type just described is disclosed, for example, in Japanese Patent Laid-Open No. Hei 3-200909 (hereinafter referred to as Patent Document 2).
The image pickup lens disclosed in Patent Document 2 is formed as a lens of the rear focus type wherein, when the image pickup object distance varies from the infinity to the proximity, the first lens group is fixed with respect to an image surface while the second lens group moves from the image side toward the object side to carry out focusing.